HERE COMES Valentine's Day. If you leave dinner reservations to the last minute, you could be shut out of some of Silicon Valley's most romantic restaurants and forced to settle for something less-than-amorous, like all-you-can-eat prime rib. Here are five suggested romantic restaurants to preserve your chances for post-prandial lovin'. They're small, cozy and intimate. The food is quite good, too. And if you don't have a date for the Valentine's Day, well, these are places to avoid.